Julius-Kühn-Archiv (Mar 2012)
Why has Terbuthylazine become the basic component of weed control in maize cropping of Central Europe? A benefit assessment
Abstract
Terbuthylazine was used for weed control in German maize cropping in 2011 on nearly 86 % of total maize acreage. The ongoing success of this 45 year old herbicide can be explained by the various features for its use in maize as well as by responsible handling and care. Characteristic features of terbuthylazine are a broad controlled weed spectrum, superior residual activity, application timing flexibility from pre- to late postemergence, excellent crop tolerance, low soil mobility, perceivable speed of efficacy and suitability as partner for other active ingredients. Thanks to its combinability, terbuthylazine has maintained its importance in maize cropping, although the ubiquitous occurrence of triazine-resistant biotypes always has to be expected. In a weed monitoring in Germany and Austria in the 2008 and 2009 field season, the broad controlled weed spectrum and the efficacy of terbuthylazine in mixture with the 4-HPPD-inhibitor mesotrione on triazineresistant weed biotypes have been proven comparatively. 4-HPPD-inhibitors are preferred mixture partners due to their physiological synergism in combination with terbuthylazine. This feature enables a reduction of use rate of both terbuthylazine and mixture partner. Targeted post-emergence application of optimized pre-mixture herbicides achieves enhanced reliability and a noticeable increase of speed of efficacy. Combinations of terbuthylazine and residual graminicides offer the advantage of an all-embracing control of grass and broad leaved weed flora in maize by one pass only. Terbuthylazine is also effective against weeds not controlled adequately by other maize-selective herbicides. For reasons of preventative ground water protection, since 1991 a targeted management of the active ingredient terbuthylazine is carried out by manufacturers and registration holders. It envisages a limitation of terbuthylazine usage in maize only, one use per season in mixture with other active ingredients in spring only, and a maximum use rate of 750 g/ha. For treatments in areas with vulnerable groundwater situations (e. g. in open exposed Jurassic Karst formations) other herbicides than terbuthylazine containing products are strongly recommended. These measures have been demonstrated to be successful; in case of consequent compliance with these stewardship measures terbuthylazine can be continuously used as basic active ingredient in chemical weed control in maize for the future, maintaining all the advantages of this active substances for agriculture in Europe.
Keywords
